As a memory system used in a computer system (hereinafter, computer), an SSD (Solid State Drive) on which a nonvolatile semiconductor memory such as a NAND-type flash memory (hereinafter, simply, NAND memory) is mounted attracts attention. The memory system such as the SSD has advantages such as high speed and lightweight compared with a magnetic disk device.
Typically, a required performance of the computer to the memory system in read/write processing is different largely depending on specifications of the computer itself, a user, and a usage environment of the user. On the other hand, the speed in the read/write processing is fixedly set on the memory system side in most cases. Therefore, for a user who does not need a maximum value of the read/write processing in the specifications of the memory system, the specifications of the memory system exceed the requirements, so that the computer is not always optimally configured in power consumption or the like.
On the other hand, for example, Japanese Patent Application Laid-open No. 2009-251888 discloses a technology for the memory system that operates with a desired current consumption by changing the speed of the read/write processing based on a command from the computer. With this technology, the computer needs to have specifications to issue the command.